In a bowl, combine minced lemongrass, minced garlic, soy sauce, fish sauce, brown sugar, and a pinch of salt and pepper. Add the beef sirloin and coat well. Marinate for at least 30 minutes.

Prepare the Vegetables

Julienne the carrots and daikon radish. Slice the cucumber. Set aside.

Grill the Beef

Preheat the grill to medium-high heat. Brush the grill grates with vegetable oil. Grill the marinated beef for about 4-5 minutes on each side, or until cooked to your desired doneness. Remove from the grill and let it rest for a few minutes.

Toast the Bread

Cut the ciabatta in half and toast it on the grill for 1-2 minutes until golden brown.

Assemble the Banh Mi

Slice the grilled beef thinly. On the toasted ciabatta, layer the sliced beef, julienned carrots, daikon, cucumber slices, and cilantro leaves. Optionally, add more salt and pepper to taste.

Serve

Serve the grilled lemongrass beef banh mi immediately while warm, with extra vegetables on the side if desired.